The proposed study, a response to PA-06-257, will develop tests for use in epidemiologic studies of vestibular and balance function, and other applications in which comprehensive vestibular testing is not possible. This study will meet the requirements of the Program Announcement with the following specific aims: 1) Equipment and test development. Develop a battery of screening tests that are sensitive and specific to vestibular disorders. To meet the practical needs of future population-based epidemiologic studies, this test battery will be brief, i.e., taking less than 15 minutes, and will be performed in a space no more than 8 X 1 m. Tests of standing and walking balance and dynamic visual acuity will be included. We will develop new versions of existing tests, and will include technological development, i.e., programming new software for tests and use of head-mounted sensors, testing all apparatus for safety. We will also develop norms for all tests. This aim is largely technologically driven, not hypothesis driven. 2) Validate the new battery of screening tests. 2A) Determine if these screening tests differentiate normals from the same normals when they are given galvanic vestibular stimulation to simulate acute vestibular impairment. 2B) Determine if normals who are well trained to perform at a high level despite distraction and discomfort, i.e., United States Marines, show differences on the new test battery when tested with and without galvanic vestibular stimulation. 2C) Determine if these screening tests differentiate normals from patients with known vestibular impairments. 2D) Determine if these balance tests differentiate patients with vestibular impairments from patients with lower extremity peripheral neuropathies. 3) Estimate prevalence of vestibular impairment in two adult populations and determine if the new screening battery, i.e., the 3 screening tests plus 2 other well-validated tests, detects vestibular disorders in those populations. 3A) Determine prevalence of vestibular disorders and sensitivity of the screening battery in a sample of the general population recruited from a general medical clinic. 3B) Determine prevalence of vestibular disorders and sensitivity of the screening battery in a sample of high-functioning people in high-risk occupations recruited in a military health clinic. 4) Determine if these screening tests are sensitive to change after vestibular rehabilitation. Subjects will be tested before and after a month of vestibular rehabilitation. The vestibular system may be assessed with a wide range of objective diagnostic tests in laboratories in hospitals, tertiary care centers or even smaller clinician's offices, when space, complex equipment and staff may be available to accommodate the physician's request for diagnostic data and the unique needs of each patient. Sometimes, however, such a comprehensive test battery cannot be given due to constraints of funding, space, and/ or time. In this study we will develop and validate screening tests of the vestibular system that will be useful to testing large numbers of people by busy staff who will not be vestibular or balance specialists and whose work will be constrained by limited time, space for testing, and funds for equipment. PUBLIC HEALTH RELEVANCE: The vestibular system may be assessed with a wide range of objective diagnostic tests in laboratories in hospitals, tertiary care centers or even smaller clinician's offices, when space, complex equipment and staff may be available to accommodate the physician's request for diagnostic data and the unique needs of each patient. Sometimes, however, such a comprehensive test battery cannot be given due to constraints of funding, space, and/ or time. In this study we will develop and validate screening tests of the vestibular system that will be useful to testing large numbers of people by busy staff who will not be vestibular or balance specialists and whose work will be constrained by limited time, space for testing, and funds for equipment.